Electrostatic continuum

Simonson, T., Macromolecular electrostatics continuum models and their growing pains, Curr. Opin. Struct. Biol. 2001,11, 243-252... 

B. Mennucci, R. Cammi and J. Tomasi, Analytical free energy second derivatives with respect to nuclear coordinates complete formulation for electrostatic continuum solvation models,... 

The same subdivision is used in the qualitative discussion of ionic solvation energies, and it is found that the outer-sphere part is satisfactorily predicted by electrostatic continuum theories (as reviewed in Section III), whereas the inner-sphere part is best obtained by considering the distortion of individual bonds, using force constants from vibrational spectroscopy. 

They have compared the reaction energy profiles of five different reaction paths, including oxidative insertion, nucleophilic substitution, and single-electron transfer mechanisms involving radical species, both in the gas phase as well as using an electrostatic continuum model to include the effect of a solvent in an approximate fashion (Structures 3-5). 

The modeling of the environment can be flexible, e.g. it can be modeled through microsolvation by explicitly adding some solvent molecules or through a polarizable electrostatic continuum model. 

FF scoring most often relies on the nonbonded interaction energy terms of standard force fields, e.g., in vacuo electrostatic terms (sometimes modified by scaling constants that assume the protein to be an electrostatic continuum) and vdW terms [22,105,128,129]. As an example, DOCK and GREEN [130] have implemented the intermolecular terms of the AMBER energy function [103,104] with the exception of an explicit hydrogen-bonding term [42] ... 

While a partly classical inner-sphere contribution to the activation energy in cases where the electrostatic continuum approximation applies has been assumed by Marcus for a redox-type (i.e., non-atom-transfer) process, no successful efforts have been made to describe the instantaneous radiationless electron transfer mechanisms for heavy nuclei (see, however. Ref. 78). Overall, it seems reasonable to conclude that the instantaneous transfer theory is an unlikely hypothesis for combined atom and electron transfer. A more reasonable approach is dependent on the fact that the lifetime of an activated molecule (i.e. the proton tightly bound to its neighboring water molecules, e.g., in 11304" ) is very long compared with the transition time for one single-electron passage. 

Calculations of A<, from the electrostatic continuum model and from quantum mechanical models have been reviewed and compared/ The distinction between electrostatic displacement D and field E is emphasized. Values of A are compared for different physical models of the reacting molecules, e.g., conducting spheres (the model usually considered in previous literature) and cavities of various dimensions. In the electrostatic model a formula for A has been given, which applies to any system which has a symmetrical binuclear structure, and from which Marcus two-sphere " and Cannon s ellipsoidal " models can be deduced as special cases. 

In 1991, Kharkats and Ulstrnp calculated the Gibbs solvation energy profile for a sharp interface nsing a simple electrostatic continuum model [25]. The gist... 

For the evaluation of there are several formulas based on the shape and size of the solute and on different parameters of the solvent surface tension [43], surface tension with macroscopic correction [44], isothermal compressibility [45] and geometrical parameters of the solvent molecules [46]. The first three techniques follow the same philosophy. They do not rely on a detailed description of the discrete solvent and make use of experimental bulk parameters of the solvent, in analogy with the dielectric constant of the electrostatic continuum model. As an example of this kind of approach we present Sinanoglu s formula [44]... 

The Debye—Huckel treatment is based on continuum electrostatics. Continuum solutions are composed of ions distributed throughout a continuum solvent, w, which has no molecular structure but has a solvent dielectric strength, E. The solvent dielectric strength is completely independent of the type and/or amount of solute molecules in the continuum solution. 

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